IYPT 1990, Задачи на турнира — Задача 16. Interference

Problems for the 3rd International Young Physicists’ Tournament

Critical edition

Olympiets Youth Center, Moscow, Soviet Union; June 7‒14, 1990 [1]

Critical edition: translated, restored, and commented text [2]

FINAL DRAFT. — Please do not re-publish. Suggestions and criticism welcome

Translated, edited and commented by Ilya Martchenko. The original edition’s historical notes, sources and acknowledgments are retained with problem 1.

Епиграф

Victories do not attract him.
For him growth means: profound defeat
at the hands of ever greater adversaries.
R. M. Rilke [3]

Условие

Take two photo plates (9×12 cm), well-washed from emulsion. If they are tightly pressed (lapped) one to another, the interference bands can be observed in the reflected light. If the plates are laid on the table and the upper one is pressed in the middle part with a finger, the interference pattern looks like concentric circles. When the finger is removed, the circles “run away” from the centre. Carry out such an experiment and explain the observed phenomena. Evaluate theoretically how fast do the circles “run away” as the loading is removed.

Решение

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Оригинал в Архива: 1990.pdf